Researchers offer UK ‘ghost ponds’ new lease on life

29 July 2014

CIFOR — Resurrections can be a messy business, especially when they involve the restoration of fragile ecosystems lost in long-ago pond burials.

The British countryside was once peppered with ponds that were buried amid post-World War Two pressures to expand arable farmland and boost food production.

As luck would have it for Emily Alderton, a doctoral candidate in the department of geography at University College London (UCL), it turns out that it is difficult to completely erase a pond from the landscape.

Often a damp depression will remain — the ghost of a former pond.

Resurrecting such ghost ponds not only provides opportunities to create new habitats for wildlife, improve landscape connectivity and ease problems with water shortages, it can also help restore genetic and species diversity, said Alderton whose work on the Ghost Ponds Project forms the basis of her PhD research.

“Ghost ponds contain the buried sediments, seeds and eggs of the former pond community and by re-excavating these sites we’re opening up exciting possibilities for resurrecting lost species,” she said.

“The dormant seed bank of a ghost pond could help locally lost populations of plants to re-establish, increase regional diversity, and help create ponds which are better buffered against invasive species.”

Previous research has shown that ponds are important hotspots for biodiversity, supporting as many as 80 species listed in the UK Biodiversity Action Plan (BAP), which was established in response to the 1992 Convention on Biological Diversity, Alderton said.

“At a regional scale, ponds contribute more to aquatic biodiversity than any other water body type,” she added. “Farmland ponds in particular can be especially important, providing both aquatic and terrestrial wildlife with ‘stepping stones’ across an otherwise fairly inhospitable landscape.”

Alderton, who works with a team of researchers, including ecologists Carl Sayer, Jan Axmacher and Steve Lambert, shared her insights. 

Q: Why are you undertaking this project?

A: The reason that ghost ponds are of particular interest to us is two-fold; Firstly, there’s great potential for the buried seed and egg banks of these ghost ponds to be resurrected, bringing back locally lost species, improving genetic diversity, or simply speeding-up the pond colonisation process.  These exciting possibilities have never before been investigated.

Secondly, ghost ponds could provide a great way of getting more ponds into the farm landscape, without compromising crop yields too much.  Because ghost ponds often remain as damp, poor-quality patches of soil, they could provide greater financial rewards for farmers once restored and in a stewardship scheme, than would low-yield patches of field.  This makes re-digging ghost ponds a potentially easier sell than digging new ponds, an important consideration if we aim to protect our farmland wildlife in the long run.

Q: What is your inspiration for this kind of work?

A: The inspiration behind the Ghost Ponds Project begins at Manor Farm in the county of Norfolk, where Richard Waddingham’s dedication to protecting wildlife while running a successful farming business, showed that agricultural ponds can offer fantastic conservation opportunities and that, when approached in the right way, such conservation need not interfere overly with farming practices.

Manor Farm contains around 40 ponds, which between them support 20 species of aquatic plant, 37 species of water beetle, and 19 species of dragonfly.  More than half the ponds support breeding populations of great crested newt (Triturus cristatus), a BAP species.  The reason the ponds are so diverse is that Richard manages them, restoring three to four ponds each year to re-set their succession.  Trees are removed to allow light into the pond, and large quantities of old pond sediment are removed by digger, and spread on the fields.  The removal of sediment is especially important, as it helps bring dormant layers of the seed bank to the surface, allowing these species to re-establish.

I first visited Manor Farm in 2011, during my MSc at UCL.  By this time, my supervisor Dr Carl Sayer and PhD student Helen Greaves had been monitoring the ponds on the farm for several years, investigating how management affects biodiversity.  It seemed that re-establishment from the seed bank in restored ponds was playing an important role in their colonization.  From this starting point, we began to wonder whether the seed bank buried in in-filled ponds might act in the same way, and whether it might allow us to not only bring back these lost ponds, but also their lost communities.

Q: What is the purpose of the research?

A: The Ghost Ponds Project aims to answer the question: “Can the dormant seed and egg bank buried within in-filled ponds be brought back to life, restoring lost pond communities to the landscape?”

This is an exciting topic which has never before been investigated, and which could have important consequences for aquatic conservation.  If ghost ponds can be “resurrected”, re-activating the buried seed and egg bank by re-digging the pond, then this is a fantastic conservation resource.  Across the UK there are many thousands of ghost ponds, each one a time capsule for aquatic species.  If these can successfully be brought back to life, we can improve aquatic species abundance and connectivity, as well as species and genetic diversity.

So far, our initial findings are very promising, with a range of aquatic plant and zooplankton species being resurrected from the historic pond sediments.  The oldest ghost pond, which we’re studying was filled-in during the 1850s, but even in this pond we’ve had several species of pondweed (Potamogeton), and stonewort (Characeae), germinating from the sediments.

Q: What have you learned by doing this project so far?

A: Although the Ghost Ponds Project has only been running for a year, we’re already finding some exciting results.  We’ve found a range of aquatic plant species that are capable of resurrecting from the ghost pond sediments, including broad leaved pondweed (Potamogeton natans), curly leaved pondweed (Potamogeton crispus), and stonewort species (Charaeace).  Zooplankton, including the water flea Daphnia magna, have also come back to life after lying dormant in the buried ponds.  Further germination trials and seed viability tests should reveal more about which species are returning to the ponds, and why some have been more successful at resurrecting than others.

Q: How can these findings be applied to different types of landscapes?

A: The biodiversity value of ponds, whether in farmland, natural wetlands, urban areas or coastal sites, has been widely recognised.  Pond loss is a global issue, with studies being published in countries including the UK, Spain, France, and the United States.

With growing political and public concern over issues ranging from water security, to landscape biodiversity loss, ponds are likely to have an important part to play in future conservation efforts.  By showing that the seed and egg bank of ghost ponds can remain viable, quite possibly for centuries after the ponds have been lost, we hope to highlight the great potential for resurrecting these lost ponds to the landscape.

The scope of “resurrection ecology” stretches far beyond ponds – there have already been studies conducted into the role of dormant seed banks in restoring lakes, rivers, wetlands and rainforests.  Perhaps what makes the potential of ghost ponds especially interesting is their diversity – even ponds within a few meters of each other often contain very different communities, so by resurrecting these small pockets of diversity we could create a wonderfully complex network.

ADDITIONAL READING

For information on the findings of the Ghost Ponds Project so far, and updates on the progress of the ponds, please visit the Ghost Ponds blog.

Potential role of propagule banks in the development of aquatic vegetation in backwaters along navigation canals

Farm Ponds as Potential Complementary Habitats to Natural Wetlands in a Mediterranean Region

The Effect of Distance from Forest Edge on Seed Rain and Soil Seed Bank in a Tropical Pasture

Seedling emergence from seed banks of 15 New Zealand lakes with contrasting vegetation histories

Historical Changes in the Distribution and Abundance of Constructed Ponds in Response to Changing Population Density and Land Use

Level-dependence of the relationships between amphibian biodiversity and environment in pond systems within an intensive agricultural landscape

Managing Britain’s ponds – conservation lessons from a Norfolk farm

The relationships between soil seed bank, aboveground vegetation and disturbances in an eutrophic alluvial wetland of Western France

Countryside Survey: Ponds Report from 2007. Countryside Survey Technical Report, (7/07).

Pond biodiversity and habitat loss in the UK

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